A number of novel neurogenetic diseases have been identified by studies carried out under this project. Genetic linkage studies are underway in familial diurnally variant dystonia associated with low CSF biopterin levels and a beneficial effect of supplemental biopterin has been documented in one of these patients. Corrective therapy has been developed for autonomic nervous system dysfunction associated with Fabry's disease. Potential metabolic alterations in the Lennox-Gastaut syndrome have been examined. The incidence of seizures and cataplexy has been determined in patients with Type C Niemann-Pick disease. The effect of modifying dietary cholesterol and the responses of patients to drugs that alter cholesterol synthesis are under investigation in this disorder.